Method of boring tunnels.



N; EBBLEY.

METHOD 0F BORING TUNNBLS.

APPLICATION FILED 0GT.10,1911.

1,032,049. 4 Patented July 9, 1912.

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Patented Ju1y9,1912.

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N. EBBLEY.

METHOD 0F BORING TUNNELS.

APPLIOATION FILED ocT. 1o,1911.

Patented July 9, 1912.

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N. EBBLEY.

METHOD 0F BORING TUNNELS.

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N. EBBLEY.

METHOD 0F BORING TUNNELS.

APPLICATION FILED ooT.1o,1911.

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N. EBBLEY.

METHOD 0F BORING TUNNELS.

APPLICATION FILED 00T.10, 1911.

Patented July 9, 191.2.

'7 SHBETS--SHEET 7.

c. n N. o T n m n s A w o. c H P A m m N L n m m u L n c NORMAN EiBLEY, or WALLACE, IDAHO.

METHOD OF BORING TUNNELS.

Original application iiled April 26, 1910, Serial No. 556,667.

Serial No. 653,827.

To all whom t may concern Be it known that I, NORMAN EBBLEY, of "Wallace, Idaho, have invented new and useful Improvements in Methods of Boring Tunnels, which invention is fully set forth in the following specification.

This invention relates to a method of boring tunnels in rock format-ions and particularly in very hard rock, and has for its object to materially increase the rate of advancing tunneling operations particularly through the hardest format-ions while effecting economy in the cost of the work and comfort and convenience to the workmen while the work progresses.

I-Ieretofore, it has been proposed to drill holes in the face of the rock and to blast down the face; it has also been proposed to mill oft the face of the rock; while in other instances annular channels have been drilled in the rook and the intervening ribs between the channels have been broken down by the use of wedges or similar devices. It has also been proposed to disintegrate or weaken the rock by the application of heat, and then complete the operation by suddenly chilling the rock, as by the use of cold water, or by hammering. All of these methods of operation are slow and more or less inetlicient and expensive to operate. In addition to the diiiiculty of disintegrating or breaking up the rock along the line of the tunnel or other excavation, there arises the difficulty of removing the debris made up of the drilled and broken rock, which debris is technically known in the art as muck. In most of the operations with which I am familiar, the removal of this muck necessitates a discontinuance of the operation of disintegrating the rock while the muck is being removed, so that the disintegration and the removal of the muck go on each intermittently, the one alternating with the other.

In my companion application filed April 26th, 1910, Serial No. 557,667, of which this application is a division, I have described in detail one form of apparatus `for carrying my process into effect and so much of this apparatus will be herein described as is necessary to enable a proper understanding of the present invention. No claim is made herein to the apparatus described, as the same forms the subject-matter claimed in the application above referred to. While I Speccation of Letters Patent.

Patented July9, 1912.

Divided and. this application filed October 10,

prefer to use this apparatus in carrying out my process, yet the process may be carried out by other apparatus and is not limited thereto.

`With the above objects in view, the invention resides in general in sinking in the face of the rock to be t-unneled one or more circular channels, preferably by means of a revolving head, provided with a series of pneumatically operated drills adapted t-o cut the desired grooves or channels in the rock and then removing the rock located between the channels thereby weakened by subjecting the rock between and bordering the edges of the channels to crushing blows such as may be secured by means of fluidpressure operated hammers. The detritus resulting from these operations is removed by a mucking device as rapidly as it collects at the face of the tunnel head. rIhese and other details of procedure will be more fully explained in connection with the means for carrying out the process.

Referring to the drawings: Figures 1, la, are separated views principally in elevation and part in broken section, showing a tunneling machine embodying my improvements; Fig. 2 is a perspective detail view of a drill support; Fig. 3 is an enlarged sectional detail view showing the interior construction of a portion of the machine drillhead; Fig. l is a horizontal sectional view on the line 1 4 of Fig. 11, showing the inlet valve and ports in the engine for operating the muck shovel; Fig. 5 is a vertical sectional view on the broken line 5 5, Fig. 11, showing means for controlling the eX- haust of said engine; Figs. 6 and 6a are separated plan views of the tunneling machine shown in Figs. 1 and 1a; Fig. 7 is a view in front elevation, showing the revoluble head of the tunneling machine and the drilling devices mounted thereon; Fig. 8 is a rear elevational view of the same machine as it is braced against the tunnel walls; Fig. 9 is an enlarged detail plan view of the muck-shovel operating engine, showing a portion of the shovel attached thereto; Fig. 10 is a perspective det-ail of the controlling means for the inlet and exhaust valve of the muck-shovel engine; Fig. 11 is a vertical transverse sectional view on the line 11-11 of Fig. 9. I

Referring more particularly to Figs-1, 1a

and 8 of the drawings, the tunneling machine comprises a tool-supporting head 1 mounted on a revoluble and extensible tubular shaft 2 which is supported in front in a bearing 3, and at the rear in a supporting saddle 4, both of which supports are mount-- ed on wheeled trucks 6 ruiming on rails. The rear of shaft 2 is guided in a block 7 which is mounted thereon and made fast to the walls of the tunnel bymeans of jacks 7a. rlhis block also serves as an abutment for supporting driving cylinders 3, 3, which impart longitudinal movement to shaft 2 by means of a pair of pistons therein, which are driven by compressed air or other fluid. The rods 9, 9 of said piston are made fast at their outer ends to a collar 10 which permits rotation of shaft 2, but is fast against longitudinal movement thereon. Rotation of the main shaft 2 is effected by means of an engine 11 acting through a train of gearing on the large drive gear 12 fast on said shaft. TVith this general description I will now describe in detail the structure relating to the drill-head.

rlhe drill-head includes a plurality of tubular arms 13, 14, which serve the double purpose of drill-supports and fluid-conduits, and are ar `anged radially around the forward end of the drive-shaft 2. These arms are preferably grouped in pairs, each pair lying in the same radial plane. Each of the arms 13, 14, is made fast to the wall of the shaft 2 by securing means such as by a step 15 bolted to the wall of the shaft and having` a threaded opening into which the end of the arm may be screwed. Each tubular arm 13 is in open communication with an air pipe 16 located in the axis of the drive-shaft and is supplied with air from an air pressure reservoir, notA shown. The pipe 16 is connected with each tubular arm 13 by a coupling consisting, for example, of a cap 17 screwed on the end of pipe 16 and provided with as many threaded side openings 18 as there are arms 13. Into each of these threaded openings is screwed a nipple 19 which, in the illustrations Figs. 1 and 3, telescopes a similar nipple 2O entering side openings in a cap 21 closing` the end of a tube 22 surrounding air supply tube 16 and forming about it a dead air space. The outer threaded end of nipple 2() receives a nut 23 which securely holds the parts in place. llfubular arms 14 are provided in front with perforations 14, and are in open communication with the tubular shaft, and are secured therein by steps 24 into which they are screwed. Upon the radial arms 13, 14, I support the pneumatic cylinders 25 for driving` the tools against the face of the rock. The supporting means which I have shown and which I prefer to use comprise a bar 26, Fig. 2, having tubular spring aws 27 adapted to engage arms 13 and 14 and' be clamped thereon in any desired position along the arms by suitable bolts engaging the openings 28.

A socket 29, having its axis at right angles to the axis of the tubular clamps, is provided in bar 26 for receiving an arbor 30 which is screw threaded at one end for receiving a lock-nut, and at the opposite end is fast to and supports a bracket 31 having slide grooves 32 for receiving and retaining the drill cylinder 25 which is provided with suitable shoulders, not shown, for engaging the grooves. lith bracket 31 mounted on clamp bar 26 and the latter in position on arms 13, 14, the drill cylinderl carried bybracket 31 is capable of movement in a radial plane through the axis of shaft 2, more clearly shown in Fig. 7, by means of an adjusting screw 33, having right-and left-hand threads which engage nuts 34, 35, which have pivoted connections with the bracket 31 and with a clamp ring 36 mounted on the radial arm 13. The bar 26 above described is preferably used in supporting the pneumatic cylinders operating tools working somewhat within the circumference of the bore of the tunnel, and has the socket 29 located between the clamping jaws 27, 27. r1`he socket 29 in those bars which are used for supporting drill-cylinders 25 working around the periphery of the face of the tunnel, are preferably arranged near the rear end of the bars where less angular movement of the cylinder is required. Fach of the pneumatic cylinders 25 is of the usual type and receives its air supply through hose connections 37 connecting with radial tubular arms 13 and is provided with the customary means for controlling its piston.

rEhe boring head of the machine, as stated above, is adapted to rotate and also to advance as the rock isremoved from the breast of the tunnel. While any suitable means may be employed for this purpose the one l have illustrated and prefer to use l will now describe. Mounted on the frame 5 of the tunneling machine is a prime mover 11 which may be of any preferred form, such as an engine driven by steam or compressed air. This engine, through its pitman and crank-shaft, drives small gear 38, which transmits its power through the train of gears 39, 40, 41, bevel-gears 42 and 43, power shaft 44, gear 44', to large driving-gear 12, which is fast on shaft 2, and thereby rotates the head of the tunneling machine. The head of the machine is advanced as work progresses by manipulating the cont-rolling lever 45 which acts through suitable connecting means 45 and valve means 45 to control air supply pipe 451 and the admission and exhaust of air through pipes S" for operating compressed air cylinders 8, the pistons of which are connected to the revoluble shaft 2 in the manner above described. rI he bearing 3 in which shaft 2 is free to revolve is held against longitudinal movement relatively to the said shaft by means of two collars 4S, 49, clamped to the shaft by bolts or other means. Bearing 3 is provided with leveling or adjusting screws 50 working in lugs 51, the ends of the leveling screws resting in sockets 52 fast to the frame of the machine. `When lever 45 is operated to admit air in front or rear of the pistons in cylinders S, 8, the shaft 2 is forced to move longitudinally by reason of the connections of the piston rods 9, 9, with the shaft 2, and with this movement of the main shaft the frame also moves on the track. The rear end of shaft 2 rests in a supporting` saddle 4 mounted in the top member of frame 53. This yoke is capable of being raised and lowered by means of a leveling screw 54 working in a nut 54 formed in or carried by the lower member of frame 53. The necessary lateral adjustment of the rear of the shaft 2 is obtained by means of the jack-screws 7"?, which may be turned to slide the wheels of the rear truck sidewise on their flanges, the latter being made broad for this purpose.

Referring to Figs. 6 and 7, I have shown a plurality of rock-drills 57, 58, having chisel faces and mounted on the drill-head arms 13 at diametrically opposite points,

y and so positioned radially as to cut a channel of less diameter than that of the finished tunnel. In coperative relation with these drills, hammers 59 and G0 are mounted on the drill-head and are so positioned relatively to the center of the head and to the drills that they operate on the rock on each side of the channel formed by the drills to break down the rock weakened by the channeling operation. lVith a view of gaging the diameter of the tunnel, I preferably provide the drill-head with offset drills 61, which, by means ofan elbow bend in the drive-rod of the drill cylinder, or in the drill itself, a peripheral groove is made in the rock always advancing with uniform diameter and leaving behind a practically true surface. I preferably follow up the operation of the gage drills by action of other drills adapted to give an outwardly inclined blow to the face of the rock in the vicinity of this channel, and to this end I mount on arms 13 in the rear of the advancing gagedrills one or more rock-drills similar to drills 5'? and 58 already described, but having their blows directed outward by adjustment of the drill cylinder 25. rIhe offset gage-drill determines the diameter of the tunnel and permits of the more advantageous use of the peripheral and outwardly directed drills without danger of advancing them into the adj oining rock beyond the predetermined diameter of the tunnel. I do not desire to be limted to the kind or number of drills and hammers mounted'on the head, as it is obvious that they may bevaried for different kinds of work, provided thatthe drills and hammers coperate in the manner described.

Assuming that the tunneling machine rests on its rails in front of the rock face to be tunneled, shaft 2 is brought into alinement with the axis of the tunnel by manipulating the front and rear leveling screws 50 and 55, respectively, and jack-screws 7a, 7, which latter acting against the wall of the tunnel and block 7 mounted on shaft 2, hold the machine against lateral displacement. Vith the shaft 2 in the desired posit-ion, compressed air or other fluid is admitted to power-cylinders 8, S, by manipulating lever 45 controlling the supply and exhaust valves associated with the cylinders, whereupon the piston rods 9, 9, advance shaft 2 and with it the carriage supporting the shaft whereby the machine is moved into drilling position, and is held therein against the resistance of the jacks 7, 7, and yoke 4. rIhe drill cylinders 25 mounted on their clamp bars 25 are radially adjusted to the desired angles by turning their respective adjusting screws 33. The gage-drills at the extremities of the radial arms are adjusted to give a rectilinear blow parallel with the axis of the tunnel. rIhe drills which I locate intermediate the gage drills and substantially in the same circumference as the latter are preferably radially and outwardly inclined, as clearly appears in Fig. 1. The remaining drills which are designed to cut channels in the central areas of the breast of the tunnel I may, and preferably do, incline radially to undercut one side of the channels, though they may' be directed parallel to the axis of the tunnel. rIhe hammers are so located on the arms of the head that they are capable of directing blows on the ridges between the channels formed by their associated drills. The hammer cylinders are preferably inclined in a radial direction to give a slightly slant-ing blow on the ridges. Having now alined the shaft of the tunneling machine to be coincident with the axis of the tunnel, and having positioned the drills and hammers for coperation, compressed air is admitted to supply pipe 16 which supplies the individual drill cylinder 25. This air is preferably heated as it enters supply pipe 16 and to this end I have shown an electric heating coil 46 surrounding the inlet end of the pipe. Any other means of heating may however be employed for this purpose. `Water is also admitted into the space between the outer casing 2 and inner tube 22 through a suitable inlet 55 and is delivered on the face of the rock through perforated arms 14 for the purpose of allaying dust, cooling the tools and cleaning the surface of the rock. The operator starts the drills and hammers into action by manipulating the air-valves to the cylinders 25 in the usual manner, and applies power to the main shaft to cause its rotation by starting engine 11, which act-s on the large driving gear 12, through a train of gears previously described. As the head 1 revolves, `the outline of the tunnel is determined by the circular groove cut in the breast or face of the tunnel by gage-drills 61. The rock just within this limiting channel is cut away by the outwardly directed blows of the drills which follow. The depth to which the latter drills cut into the rock is determined by the channel cut by the gage drills, and is therefore uniform. The walls of the tunnel as they are left by the gage drills are smooth and require no trimming to make the surface regular. A second channel is shown in Figs. 1 and 6, within and concentric with the first, which is produced by the action of drills 57 and 58. This channel preferably progresses axially somewhat in advance of the outer channel to compensate for the difference in rigidity of the arms 13, 14, near their attachment to the shaft 2, as compared with that near their extremities, thereby better distributing the work on the head. Finally the hammers 59 and 60 by their battering action in the rock already weakened by formation of the channels reduces the projecting ridges to the level of the bottom of the channels. As

the rock face recedes before the disintegratl ing action of this treatment, the head of the tunneling-machine is advanced by the operator in control of lever 45. Vhen the drilling head has been advanced to its extreme limit, the jacks 7 a are released and the block 7 moved forward on the shaft 2 and secured in place again by said jacks for repeating the above-described operations. Vhile any form of bit may be employed with the drills, T prefer to use a chisel bit followed by one of cross steel. This combination is very effective in breaking down very hard rock.

The continuous removal of the muck is effected by means of the muck-shovel which will now be described.

Referring to Figs. 1 and 8, the rails of the track on which the wheels of trucks 6 run, I preferably secure to a portable floor 56, made of heavy iron plates bent to conform with the curved shape o-f the tunnel. This fioor extends as far as possible to the front of the tunneling machine when the work of drilling is begun, and on this forward portion of the floor I place a muck-shovel 62, preferably of heavy steel and curved to conform to the floor 56. The length of this shovel is sufficient to extend from the front end of the carriage frame 5 to near the breast of the tunnel when the machine is in operative position. For the purpose of reciprocating the shovel 62, and to give it the desired acceleration in its to-and-fro movements, it is connected to driving means such as the piston 63 of an engine 64, by a rigid bail 65 which is bolted or otherwise secured to the shovel. The character of the reciprocating movements imparted to this shovel determine primarily its peculiar advantages.

In Figs. 4, 5, 9, 10, and 11 I have illustrated pneumatic means for securing the movement referred to, but other means may be employed such as cam-actuating means. 66 is a power cylinder provided with a piston, the movement'of which is transmitted to shovel 62 by means of a power-transmitting rod 63. The cylinder 66 is provided with a fluid inlet chest 67 and an exhaust chest 68. Tithin chest 67 is a quick acting slide valve 69 adapted to alternately bring into communication an exhaust port 70 in cylinder 66 with ports 71 and 72 therein. To secure rapid shifting of valve 69 its valve rod 73 is made of considerable length with its outer end supported in a lug or projecttion 74 on a bar forming a part of a frame 74 for supporting the various parts of the shovel driving mechanism. The end of valve-rod 73 is provided with a stop-member 75 limiting the inward traverse of the valve. Fast to rod 73 are two abutment rings 76, 77, secured thereon in adjustable position by clamping screws. A sleeve 78 loose on rod 73 sepa-rates two springs 79 and 8O and is provided with an arm 81 adapted to be clamped fast to the piston-rod 63. This rod is provided with a lug 82 in which the end of a second valve stem 83 is secured amd operates exhaust valve 84 in chest 68. Valve stem 73 is also provided with a locking means such as plate 85 having thereon two notches 86 and 87 for receiving a springlatch 88 having a rearwardly extending arm 89 adapted to be tripped by a tappet 90 mounted on piston rod 63. A second tappet 91 is also mounted on piston rod 63 to trip latch arm 89 on the return stroke of the piston. The spaces on opposite side of the piston in cylinder 66 communicate by passages 71 and 72 in the walls of the casing with the valve chest 67, and by means of valve 69 with exhaust passage 70 leading into the exhaust chest 68. The outlet opening of exhaust passage 70 is in the form of a narrow slot 92, Figs. 5 and 11. Diametrically opposite slot 92 is a narrow passage 94 either in the wall of casing 68 or in a sleeve 97 communicating with the exhaust -port 95, said passage being opened and closed by the reciprocating movement of solid piston 84.

The operation of the mucker thus' far dedescribed is as follows: With the parts in position shown in Fig. 9, the shovel 62 has been sent int-o advanced position by a previous forward movement of piston rod 63,

and it is on the point of starting back, at which time the shovel receives a slowly accelerating rearward movement for the purpose of permitting the muck on the shovel taking up the motion of the latter. As the .shovel retreats its movement it is accelerated and then suddenly stopped, permitting the muck load to continue rearward by its own momentum and is then removed by a traveling carrier while the shovel is given a sudden impetus forward into the pile of muck and shoved down near the end of its advance by action of the drivingl means. Before, however, piston rod v63 reaches the end of its outward stroke tappet 90 engages and raises latch 88, thereby releasing previously compressed spring 80 which shoots valve stem 73 forward into position for notch 86 to receive latch 88 and lock valve stem 73 in advanced position during the rearward stroke of piston rod 63. Valve 69 in valve chest 67 will then have the position shown in Fig. t during the time the piston in power cylinder 66 is moving from right to left in the figure. Compressed air entering` chest 67 through supply pipe 96 passes by way of passage 72 to the rigat side of the piston Fig. e, or the left side as viewed from the rear, as shown in Fig. 5. As the piston retreats it expels the exhaust air through passage 71 into passage T0 and by way of the gradually opening slit 92 into the chest 68 and thence through slit 9J; and port 95. The rapidity of movement of the piston rod 63 and muck-shovel 62 is therefore governed by the exhaust valve 84 which controls the exhaust from cylinder 66. The piston begins its return movement slowly because the exhaust valve S-t nearly closes the exhaust port 92. Further movement of the piston in cylinder 66, together with that of piston valve 841, gradually uncovers the exhaust port 92, permitting more rapid escape of air in the power cylinder and efecting increased speed of the piston rod 63 with its shovel 62. The speed of the shovel on its rearward trip is accelerated up to the end of the back stroke. During this period spring 7 9 has been compressed by the rearward movement of collar 81 while the valve rod 73 has been held stationary by engagement of latch 88 in notch 86. This spring is next released by engagement of tappet 91 with latch arm 89, thereby releasing valve rod 7 3 which is shot rearward by spring 7 9 and held in this position by latch 88 dropping into depression 87 till another piston stroke is effected. At the moment the piston rod 63 reaches its maximum speed it stops for reversal. The muck on the. shovel however continues by its own momentum to slide rearward to a suliicient extent to come within the action of blades on a continuous carrier 97. rlhe shovel next starts forward the moment valve 69 is reversed to admit compressed air into port 71. The exhaust valve 84 is now in position to completely uncover the exhaust passages 92 and 9st and permit rapid escape of air from cylinder 66. The piston rod 63 therefore starts with a rapid movement forward and the shovel 62 is forced under the muck in a manner similar to the operation of a hand-shovel. The shovel is slowed down as it nears the end of its travel by cutting down the size of the exhaust port 92, by valve 84. This valve, however, at no time completely cuts ott' the exhaust, but lea-ves a small opening which facilitates reversing the piston. The shovel is now in position to move rearward with its load and repeat the cycle of operations above described.

In Fig. 11 1 have shown means for regulating the size of the exhaust port 92, for further varying the character of the movement of the muck shovel. 97 is a sleeve fitting within the exhaust casing 68 and provided with two diametrically positioned slots registering with slots 92 and 9st. By means of screws 98, 99, turning in threaded openings in the wall of the valve-casing, and having their ends resting in tangential shoulders cut in the wall of sleeve 97, the latter can be given a slight rotation in opposite directions to regulate the size o-f the exhaust port 92. The sleeve is locked in any desired position by means of a set screw 100.

The muck shovel 62 brings the muck well to the rear of the drill head where it is scraped off by a traveling conveyer 97 provided with blades 101. rIhis conveyer may be of any approved form, though l prefer the one herein shown and described, which consists of two endless sprocket-chains 98 running around sprocket wheels 102 mounted on the frames at its rear and in front, around sprocket wheels 103 mounted on an axle 104k having bearing in arms 105 which are hinged to depending brackets 106 fastto the frame 5. The free ends of the arms 105 are held in a normally horizontal position by retaining means, such as by links 107 engaging projections 108 on the arms 105. Scraper blades 101 are secured between the chains, and one or more guide wheels 109 are mounted on the frame to direct the chains. Movement is given the endless chains by means of an engine 110 which drives a gear 111 meshing with a large gear 112, which latter drives sprocket-wheel 102 through a chain 113 and sprocket-wheel 114 fast to the shaft carrying sprocket-wheel 102. As the blades 101 are carried by the chains down and around the forward sprocket-wheels 103 they scrape the muck from shovel 62 onto floor 56 on which also the rear portion of the shovel 62 slides. Each mass of muck delivered thus to the carrier is worked back on the smooth iron floor 56 and delivered to a belt 115 or other means whereby it may be delivered out of the tunnel. Should perchance the blade of the traveling conveyer meet an obstruction in the shovel too large for it to readily pass under the front sprocket-wheels 103, the latter will be lifted to clear the obstruction, since the shaft 10A on which these wheels are mounted has bearings in arms 105 hinged to a fixed part of the carriage frame. Stoppage of the conveyer is thus prevented.

The operation of removing the muck debris will be readily understood from what has preceded. The shovel G2 mainly rests on the smooth iron floor of the tunnel and therefore is readily slid back and forth while its forward part hugs the ground or rock-bottom of the tunnel. The outward stroke of the drive rod G3 advances the shovel to its work with first a rapid movement in the nature of a quick shove which causes it to enter the muck and then the drive-rod rapidly slows down its movement and stops the shovel. On reverse movement of the drive-rod 03 the shovel is slowly withdrawn from the pile for a fraction of the piston stroke and as the load of muck takes up the movement of the shovel the momentum of the whole is increased to its maximum at the end of' the traverse of the shovel where the latter is brought to a sharp stand-still and again shot forward. The muck, however, by reason of its own momentum, continues to the rear, more readily slid ing over the shovel as the latter moves in the opposite direction, and is caught under the blades 101 of the conveyer which force it to the rear en the smooth iron floor 56.

This operation of muck removal is continuous and effective. The parts of the device are readily assembled for purposes of cleaning, removal of obstructions, and of making repairs, while it is simple and cheap 'inconstruct-ion.

lhat is claimed is 1. A method of drilling tunnels in rocks or other hard material, consisting in sinking in the face of the rock one or more channels and removing the rock weakened by said channels by subjecting the face of the rock bordering said channels to crushing blows.

2. A method of drilling tunnels in rock or other hard material, consisting in sinking in the face of the rock a circular channel normal to the cross-section of the tunnel and of the diameter of the finished bore, and then subjecting the rock within this space to simultaneous drilling and hammering to dislodge the same.

3. A method of drilling tunnels in rocks or other hard material, consisting in sinking in t-he face of the rock a plurality of circular channels one of which is of the diameter of the finished bore and subjecting the rock remaining between said channels to crushing blows to dislodge the same. i

t. A method of drilling tunnels in rocks or other hard material, consisting in sinking in the face of the rock a plurality of circular channels one of' which is of the diameter of the finished bore and subjecting the rock remaining between said channels to crushing blows to dislodge the same and simultaneously removing the disintegrated rock.

ln testimony whereof I have signed this specification in the presence of two subscribing witnesses.

NORMAN EBBLEY. Witnesses L. C. lVLsoN, Crras. B. Hor'r.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents, Washington, D. C. 

